The present invention relates to mobile irrigation systems for agricultural fields. More particularly, the present invention relates to irrigation systems using a plurality of movable towers and a water supply pipe extending between the towers.
A common type of movable-tower irrigation system is referred to as a pivot irrigation system. A typical pivot irrigation system includes a plurality of towers. Each tower includes a frame with wheels mounted at the bottom of the frame and a motor arranged to drive at least one of the wheels. A water supply pipe extends from a fixed center pivot across the tops of the towers. Numerous sprinkler pipes are connected to the water supply pipe. In operation, the motors of the towers are actuated to drive the wheels so as to move the towers in a. As the towers move, the supply pipe swings around the center pivot 18. This motion is accommodated by a rotary coupling at the center pivot, which allows the supply pipe to swing in an arc or circle around the center pivot. Thus, each tower moves along an arcuate path such as a circle or part of a circle around the center pivot.
Systems of this type are widely used in large-scale agricultural irrigation. Such a system may include numerous towers and the water supply pipe may extend over a length of hundreds of feet. A large system of this type can irrigate a field of tens or hundreds of acres. Because the water supply pipe is carried at the tops of the towers, it passes over the crop growing in the field without damaging the crop. However, the crop typically does not grow in the tracks formed by the wheels of the towers, because the wheels will crush the growing plants.
Each tower is designed to have a relatively small width in directions transverse to the direction in which the tower moves. For example, the tower may include only two wheels arranged in a single row so that both wheels travel in the same track. The narrow structure allows the tower minimizes damage to the crop growing along the sides of the track, and allows the tower to move along the track without being blocked by the crop.
As the system operates, the wheels repeatedly traverse over the ground in the tracks while the ground is being moistened by the water applied to irrigate the crop. The wheels can form ruts in the ground at the tracks. As the ruts deepen, the wheels of one or more towers may become stuck in the ruts. When this occurs, the tower, the supply pipe or other elements of the pivot irrigation tower may be damaged. Also, when a tower is stuck, the farmer must travel out into the field and pull the tower from the rut using equipment such as a tractor or truck. This results in damage to the crop in the field and a considerable waste of time and labor. Moreover, the ruts can cause damage to other farm equipment that travels across the field. Considerable effort has been devoted in the art to solving this problem. However, no truly satisfactory tower has been found heretofore.